Integrated Computational Materials, Process and Product Engineering – IC-MPPE 2022

Oxide-dispersion strengthened materials exhibit improved high temperature mechanical properties such as strength and creep resistance. However, their production via mechanical alloying is not only time-consuming and thus expensive but also in some cases difficult to implement. Therefore, in order to improve the efficiency of the mechanical alloying process, cryomilling was investigated for the production of oxide-dispersion strengthened alloys. For this purpose, milling was performed at room temperature and at cryogenic temperatures in a novel attritor ball mill using prealloyed fcc FeCrMnNiCo powders together with 1 wt.% yttria. Detailed investigations of the as-milled powders include X-ray diffraction and high-resolution scanning electron microscope as well as atom probe tomography, transmission electron microscopy and positron annihilation spectroscopy have been performed. The as-milled powders indicate an increased milling efficiency of cryomilling towards shorter milling times necessary to refine and dissolve a substantial amount of yttria but also yielded a more homogeneous yttria distribution for cryomilled powders at the same milling time. Nano-scaled and atomistic examinations suggest a vacancy assisted dissolution of yttria into nanoclusters. Furthermore, the replacement of yttria with metallic yttrium was examined in order to bind and reduce excess oxygen incorporated during the process. These experiments using a Fe-10Al-4Cr-4Y2O3 alloy were carried out under vacuum using a conventional ball mill and were mechanically tested in the consolidated state exceeding the creep resistance of the high-end Ni-based superalloy as CMSX single crystals at temperatures beyond 1100°C.